If you are using Western languages with the Latin character set you will generally not have any problems with font rendering in your PDF files, unless the fonts you use in your project are not installed on the user's computer. If that is likely, you should embed the fonts in the PDF document with the settings in Configuration > Publishing Options > Adobe PDF > Font Embedding. See Font Embedding for details.
If the text in your PDF looks strange, with some characters displayed incorrectly and odd spacing between the characters the culprit is most probably the printer driver used to generate the PDF document. To fix this, go to View > Program Options > PDF and select a different driver for your PDF output.
On current versions of Windows you will generally get good results with the Microsoft XPS Document Writer driver, which is always present. Customized drivers from printer manufacturers often cause problems, however. If you experience this, try installing one of the standard printer drivers included with Windows. To do this, just add a new printer in the Windows Control Panel, then choose that printer as your PDF reference driver in Help+Manual. You don't have to have the physical printer to be able to do this. Any recent DeskJet or LaserJet driver from the standard list will generally produce good results, and the Brother HL series laser printer drivers are also generally good.
If you are publishing a project that requires fonts with special character sets, for example for Asian languages, Russian or Greek, you may need to configure some special settings in the font embedding section of your project. See Font Embedding for details.
If you are using any kind of special characters it is very important that the font you choose to display them includes those characters. This is usually the case with modern Unicode fonts, but custom fonts often have limited character sets. Your PDF may look OK when such a font is used, but you may find that the file then becomes very large and the text cannot be selected or searched. This is because of the missing characters — when this happens, all the characters (not just the missing ones) have to be replaced with little graphics to make up for the missing support in the font. This takes up a lot of space and cannot be searched like normal text.
If you are mixing languages with the Latin character set and other languages in a single project, particularly Asian languages, it is generally advisable to use separate fonts for each language. Here too, it is essential to make sure that the fonts you use actually contain all the characters you are using in your text. A single missing character in the font can cause the text to all be rendered as glyphs (graphics), resulting in the problems described above.
See Font Embedding for detailed recommendations on this subject.